A Mexican drug cartel commander known as “Tweety Bird” pleaded guilty on Thursday in federal court in Washington to ordering the ambush and murder of U.S. immigration agents in 2011, according to U.S. officials. The plea related to a February 2011 incident when two “hit squads” from the Los Zetas drug cartel forced an armored U.S. government vehicle off a highway near Mexico City and surrounded it, federal prosecutors said.

Zetas commander Julian Zapata Espinoza, known as “El Piolin” (Tweety Bird), ordered U.S. Immigration and Customs Enforcement special agents Jaime Zapata and Victor Avila out of the car, said Acting Assistant Attorney General Mythili Raman of the U.S. Justice Department’s Criminal Division. When the agents refused, identifying themselves as American diplomats from the U.S. embassy, Espinoza ordered the gunmen to fire on the vehicle. Zapata was killed and Avila was seriously wounded but survived, officials said.